Traditional mail clients often provide users the opportunity to create one or more rules to apply to incoming or outgoing messages. These rules consist of one or more conditions and one or more actions. Traditional mail clients typically provide a fixed set of conditions and actions from which a user may create the one or more rules. For instance, a user may create a rule that plays a particular sound when the user receives a message from a particular email address. Here, the condition is that the incoming message comes from the user-specified email address, while the action comprises playing the user-specified sound. Other rules may include automatically moving incoming messages from a particular person or distribution list to a particular folder, deleting an incoming message that has particular words in the subject line, saving certain outgoing messages to a particular folder, and the like.
These rules have proven very useful in helping to manage users' mailboxes. Unfortunately, because the mail client itself provides all of the conditions and actions for these rules, the benefit of mail-client rules remains somewhat limited.